Method of manufacturing a supple,vapor- and moisture-permeable sheet material



United States Patent Int. Cl. B29tl 27/00; B 29h 7/20; B44d 1/44 U.S. Cl. 117-11 11 Claims ABSTRACT OF THE DISCLOSURE A supple, vaporand moisture permeable sheet material is prepared by treating the web with 0.1 to 20 percent, based on the weight of the web, of a bonding inhibitor, which is selected from the group consisting of (a) saturated aliphatic hydrocarbons having an alkyl group of 12 to 30 carbon atoms in the molecule, (b) saturated aliphatic alcohols having an alkyl group of 12 to 30 carbon atoms in the molecule, (c) carboxylic acid esters having at least one saturated alkyl group of 12 to 30 carbon atoms in the molecule and (d) urethanes having at least one saturated alkyl group of 12 to 30 carbon atoms in the molecule, impregnating the web with a solution of polyurethane elastomer, coagulating the impregnated elastomer in contact with a coagulating liquid which is miscible with a solvent of the solution and non-solvent for the web and the impregnated elastomer, removing said bonding inhibitor with a liquid which is a non-solvent for the web and the impregnated elastomer, and drying said web.

The present invention relates to a method of manufacturing sheet materials for the replacement of suede or the base substrate of the synthetic leathers having good suppleness, vapor and moisture permeability.

This application is a continuation-in-part of our copending application Ser. No. 429,629, filed on Feb. 1, 1965, and now abandoned.

It is well known that the method of making supple moisture-permeable sheet material which comprises the following steps in sequence, forming a web comprising synthetic fibers, impregnating said web throughout with a solution of a synthetic polymer, extracting substantially all of the solvent from the impregnating solution by treating the impregnated web with a liquid which is miscible with the solvent of said solution and is a noneolvent for said fibers and said synthetic polymer, and drying the impregnated web, whereby the impregnant is deposited throughout said web in the form of a matrix for said fibers and a matrix has a spongy microporous structure. The obtained sheet material by the abovementioned process using a random and needle punched web consisting of polyamide fibers or polyester fibers as a web, dimethyl formamide solution of polyurethane elastomer as a solution of synthetic polymer and water as a liquid which is miscible with the solvent of said solution and is a non-solvent for said fibers and said synthetic polymer is supple, but it is not satisfactory for the consumers to the replacement of natural leather to use the shoe-upper and leather cloths at the point of suppleness. Said material is still more stilt compared with the natural suede.

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Examination of said material under high powered microscopy revealed that the impregnated and coagulated matrix is adhered about the web fibers, as shown in FIG. 4 of U.S. Patent No. 2,972,554.

According to our careful investigation for the shortcoming of said sheet material, it is considered that the suppleness of the sheet material depends on the extent of adhesions among the web fibers and the coagulated matrix. The greater the extent of adhesions are presented in the web, the poorer supple sheet material is obtained. Therefor, it is possible to overcome the shortcoming of said material by preventing the occurrences of adhesions among the web fibers and the matrix, or by destroying the temporary adhesions among web fibers and the matrix.

In accordance with the present invention, the supple sheet material is obtained by treating the web with the bonding inhibitor and removing said bonding inhibitor after the step of coagulating the impregnated polyurethane elastomer with a non-solvent for said elastomer and the web fibers.

Suitable bonding inhibitor used in the present invention may be mentioned;

(a) Saturated aliphatic hydrocarbons having an alkyl group of 12 to 30 carbon atoms in the molecule, such as dodecane, tridecane, tetradecane, pentadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, octacosane, docosane, tricosane, tetracosane, octacosane, nonacosane, tricosane and saturated aliphatic isomers thereof. Paratfin wax, which is comprising the mixtures of saturated aliphatic hydrocarbons having from 12 to 20 carbon atoms, also, may be used in the present invention.

(b) Saturated aliphatic alcohols having more than 12 and less than 30 carbon atoms, such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, eicosanol, decanol-Z, tridecanol-2 and isomers thereof.

(0) Carboxylic acid esters having at least one saturated alkyl group of 12 to 30 carbon atoms in the molecule; such as the reaction products of carboxylic acid and saturated aliphatic alcohols having more than 12 and less than 30 carbon atoms, for example tetradesine capronate pentadesine capronate, octadecyl laurate, dodecyl palmitate, octadecyl palmitate, or melissyl palmitate, the reaction products of saturated aliphatic carboxylic acid having an alkyl group of from 12 to 30 carbon atoms and alcohols, for example, heptyl myristate, heptyl palmitate, octyl palmitate, sorbitan monostearate, sorbitan mono palmitate, methyl-, ethyl-, propyl-, isoamyl-, tert. butyl-, heptyl-, octyl-, hexadecyl-, heptadecyl-, octadecy1-, oleylor hexacosyl stearate, and

.(d) Urethanes having at least one saturated alkyl group of from 12 to 30 carbon atoms in the molecule; such as the reaction products of monoisocyanate and saturated aliphatic alcohols having more than 12 and less than 30 carbon atoms, for example, undecyl a-naphthyl urethane, lauryl phenyl urethane, myristic hexamethylene urethane, pentadecyl hexamethylene urethane, cetyl tetramethylene urethane stearyl hexamethylene urethane or nonandecyl phenyl urethane, and the reaction products of saturated aliphatic monoisocyanates having an alkyl group of from 12 to 30 carbon atoms and alcohols, for example, ethyl cellulose octadecyl urethane.

The treatment of the web with the bonding inhibitor in the present invention is accomplished by treating the web with solution or emulsion of said bonding inhibitor prior to the step of impregnating the matrix into the web or by impregnating solution or emulsion of the mixture of the matrix and bonding inhibitor.

The amount of the inhibitor treated in the present invention is at the range of between 0.1 to weight percent preferably 2 to 15 weight percent, based on the weight of the web.

Suitable solvents for the bonding inhibitors to be used in the present invention are aliphatic lower alcohols, such as methanol or ethanol, aliphatic ketones such as acetone, or the solvents used in dissolving the poly urethane elastomer, such as dimethyl formamide, diethyl formamide, dimethyl acetamide, diethyl acetamide or tetrahydrofuran.

When the bonding inhibitors are used in the form of emulsion, aqueous emulsion consisting of said inhibitors, water and nonionor anion surface active agents is preferable.

The web, or needle punched web or three dimensional web to be used in the invention is the web bound together of adjacently disposed fibers lying substantially parallel to the plane of the web (or face of the web) forcibly orienting suificient fibers to a position substantially perpendicular to the plane of the web that a unitary, dense coherent structure being formed. :In the present invention, the preferred fiber orientation is accomplished by punching the web with fine, barked needles, which are mounted in conventional needle loom.

Suitable fibers used in the invention to make the web may be mentioned as follows: cotton, viscose rayon staple fiber, cellulose acetate fiber, polyamide fibers such as nylon-6 (polycaprolactam), nylon-6.6 (polyhexamethylene adipamide), nylon-7 (polyenanthamide), nylon-11 (polyundecamide) and copolyamide thereof, polyester fibers such as polyethylene terephthalate fiber and copolyester fibers mainly consisting of ethylene terephthalate segment, polyacrylonitrile fibers and polyvinyl chloride fibers.

Another type of fibers that gives more desirable sheet material according to invention are the fibers consisting of the polymer mixture of polyamides and polystyrene, and the fiber consisting of the polymer mixture of polyesters and polystyrene. The contents of polyamides or polyesters in the fibers may be regulated at the range of about 33 to 60 weight percent, respectively. Said fibers are readily made by melt spinning process from the above mentioned mixtures, as disclosed by Hiroshi Hayanami and Osamu Fukushima in US. Patent No. 3,330,899; and Takeshi Yasui, Takaakira Tsuji and Osarnu Fukushima in US. Patent No. 3,322,854, respectively.

Suitable solvents used in the invention to remove the bonding inhibitor after the coagulation of the matrix are aromatic hydrocarbons such a toluene or xylene, esters such as butyl acetate, aliphatic hydrocarbons such as heptane, gasoline or kerosene, chlorinated hydrocarbons such as carbon tetrachloride, aliphatic lower alcohols such as methanol or ethanol, aliphatic ketones such as acetone and the mixture thereof, which are non-solvent for the web fibers and the matrix.

But when the web comprises the fiber consisting of the polymers-blended compositions of polyamide (or polyester) and polystyrene, the above mentioned solvents to remove the bonding inhibitor, without aliphatic lower alcohols and ketones, may be used as the solvents to remove polystyrene from the fiber to make a hollow or perforated fiber.

Suitable impregnants or matrix used in the present invention are polyurethane elastomers which are produced from the reaction of polymer diols such as polyester diols, polyether diols or polyetherester diols, organic diisocyanate and the chain extenders, such as aliphatic diols, aliphatic and aromatic diamines or hydrazine, by various well known processes as disclosed in US. Patents 2,871,218; 2,899,411; 2,957,852 and in a copending application Ser. No. 617,511, filed Feb. 21, 1967, by Kanji Matsubayashi and Takuo Kawaguchi. Minor amount (at most 50 weight percent) of polyvinyl chloride, polyacrylic acid esters or chlorinated polyethylene may be used by mixing with said polyurethane elastomers.

Suitable solvents for the impregnants or mixture to be used in the present invention are dimethyl formamide, diethyl formamide, dimethyl acetamide, diethyl acetamide, tetrahydrofuran and the mixtures thereof, which are solvent for the elastomers and miscible in water.

The solution of the elastomer is not necessary to be a true solution, but may be an emulsion as far as it is possible to impregnate the web therewith. To the solution there may be added salts, dyestulfs, pigments, fillers and minor amount of non-solvent for said elastomer.

Suitable coagulating liquid which is miscible in the solvent of the elastomer and non-solvent for the elastomer, is water or low aliphatic alcohols such as methanol, ethanol or glycerin, but water or an aqueous solution of the elastomer solvent such as an aqueous solution of dimethyl formamide is preferred.

The coagulated impregnant or matrix deposited in the spaces between the web fibers are in a microporous form and there are substantially no adhesion between the deposited impregnant or matrix and the web fibers.

The sheet material of the present invention is eminently suited for use as a replacement of suede by bufling a side of the surface with sand paper.

The useful synthetic leathers will result from applying a flexible layer of permeable or impermeable coatings to at least one side of the obtained sheet material. Gasand moisture-permeable coatings based on polyurethane elastomers are of particular interest, such as e.g. those disclosed in US. Patents Nos. 3,000,757; 3,169,885; 3,190,- 766 and 3,348,963.

The following preferred embodiments, in which improved sheet materials are produced, are intended only to illustrate the invention and not to limit it in any way.

EXAMPLE 1 The molten mixture consisting of 45 weight percent of polycaproamide and 55 weight percent of polystyrene was spun from the nozzle having 400 holes, each 0.20 mm. in diameter, at a spinning temperature of 300 C. into an air of 30 C. to cooling the extruded filaments, by the method disclosed in US. Patent No. 3,330,899. The filaments, thus obtained, were crimped to 15 curls/inch and cut to 50 mm. in length. The web was made from said out fibers by a random 'webber and subjected to the needle punching to make a random three dimensional web having the weight of 340 g./m.

The web was impregnated with dimethyl formamide solution containing a mixture of 20% polyester urethane elastomer, which was produced by the reaction of polyethylene propylene adipate having a molecular weight of about 2000 (the molar ratio of ethylene glycol units to propylene glycol units of 09:01), p-p'-diphenylmethane diisocyanate and ethylene glycol in molar ratio of 1:5 :4 according to the method disclosed in US. application Ser. No. 617,511, 8% based on the elastomer, of stearyl alcohol and 6%, based on the elastomer, of sorbitan monostearate. The impregnated web was then passed through a pair of rollers having a clearance of 1.4 mm. to regulate the thickness of the web to 1.6 mm. and to make the surface of the web smooth. The total amounts of the bonding inhibitors treated in the web are about 14% based on the weight of the web fibers.

The impregnated web was dipped into cold water at 30 C. for 10 minutes, and then dipped into warm water to C. for 20 minutes to complete the coagulation of the impregnated elastomeric solution.

After the coagulation of the impregnated elastomer, the web was passed through pair of rollers for ten times in warm water at 70 C. for 3 hours to remove the solvent of the elastomer, and then dried.

The dried sheet material was repeatedly squeezed for 10 times through pair of rollers in toluene at 70 C. for

3 hours to remove sorbitan monostearate and polystyrene, which was a component of the web fiber.

The adhesions among the web fibers and the coagulated microporous elastomer were substantially not seen by the examination under the high powered microscopy.

The sheet material, thus obtained, had a good supple, vaporand moisture permeability, and was useful for the base substrate to produce a synthetic leather like a box-calf to make shoe-upper by coating a side of said sheet material with gas-permeable elastic polyurethane coating which was produced by the method disclosed in US. Patent No. 3,348,963.

EXAMPLE 2 The molten mixture consisting of 45 weight percent of polyethylene terephthalate and 55 weight percent of polystyrene was extruded from the nozzle having 300 holes, each 0.25 'mm. in diameter, at a spinning temperature of 300 C. into the cooling zone of air to produce the polymers-blended and spun filaments. The filaments, thus obtained, was hot stretched, crimped 18 curls/inch and cut to 50 mm. in length. The web was made from said fibers by a random webber and subjected to the needle punching to make a random web having the weight of 220 g./-m.

The web was dipped into an aqueous emulsion of the bonding inhibitor for 5 minutes, which emulsion was produced by mixing the mixture consisting 30 weight parts of ethyl cellulose octadecyl urethane, 30 weight parts of surface active agents (the mixture of nonion surface active agent and anion surface active agent at the weight ratio of :15) and 40 weight parts of water and diluting said mixture to times by weight of Water. The web was then dried. The amount of the bonding inhibitor in the web was reached to 5 percent by weight of the web fibers.

A dimethyl formamide solution consisting 6 weight percent of polyurethane elastomer, which was produced from the reaction of polyethylene propylene adipate (the molar ratio of ethylene glycol units to propylene glycol units of 0.7:0.3) having a molecular weight of about 1500 and hydroxyl groups at both ends, p-p-diphenylmethane diisocyanate and ethylene glycol (molar ratio 1:2.5:1.5) was impregnated into the pretreated web.

Excess solution was squeezed out between pressure rollers so that about 0.5 part of elastomer retained in each part by weight of the web.

The impregnated web was dipped into an aqueous solution containing weight percent of dimethyl formamide for 15 minutes to complete the coagulation of the impregnated elastomer. The web was then squeezed with pressure rollers. The web was passed with hot rollers at 100 C. to make the surface smooth, and then dried.

The sheet, thus obtained, was dipped into toluene heated at 70 C. for 5 hours to remove ethyl cellulose octadecyl urethane and polystyrene, which was a component of the web fiber. The sheet was then washed with methanol and water, and dried. A desired sheet material was thus obtained.

Examination of the obtained material under high powered microscopy revealed that very little bonding among the web fibers and the matrix. In addition very fine cavities existing at random caused by dissolving away polystyrene existed in the web fibers. As a result, the sheet material had a very soft and flexible texture and very fine appearance like a sheep skin.

The sheet material, thus obtained, was useful for the base substrate to produce a synthetic leather like a boxcalf by coating said sheet material with dimethyl formamide solution of polyester urethane elastomer, which was produced by the method disclosed in US. Patent No. 2,871,218, and then coagulating the coatings in water and drying.

6 EXAMPLE 3 The needle punched web having the Weight of 250 g./m. was made from cut fibers of polyhexamethylene adipamide having the fineness of 1.0 denier and 50 mm. in length by the same method disclosed in Example 1.

The web was dipped into an emulsion consisting 35 weight parts of paraflin wax available on the market, 35 weight parts of nonion-anion surface active agent available on the market and 30 weight parts of water and further diluted to a concentration of 1/ 10 with water. The web was, then squeezed through rollers and dried at C. The amount of paraffin wax in the web is reached to about 7% based on the web fibers.

The web, thus treated, was impregnated with a tetrahydrofuran solution of 8% polyurethane elastomer, which was produced from the reaction of poly e caprolactone having a molecular weight of 1100 and having hydroxyl group at both ends, p.p'-diphenyl methylene diisocyanate and ethylene glycol in molar ratio of 1:2:1. Excess solution was squeezed out between pressure rollers so that about 0.8 parts by weight of polyurethane elastomer was retained in each part by weight of the web.

The web was then dipped into an aqueous solution of 40 percent tetrahydrofuran for 10 minutes to coagulate the impregnated elastomer, and then dipped in water for 5 minutes to complete the coagulation of the elastomer. The web was then squeezed out between rollers, throughly washed with water and pressed by hot rollers to dry.

Wax was then removed by hot toluene. The web was washed with methanol and then with water, and dried.

The sheet thus obtained was soft, compact and had a texture similar to that of cow hide, i.e., covering leather.

EXAMPLE 4 The needle punched web having the weight of 220 g./m. was made by the same method of Example 1 from the mixtures of 20 percent, by weight of polyvinyl chloride fibers, which had the fineness of 2.0 denier and 50 mm. in length, and 80 percent, by weight of the fibers, which was produced from the same method disclosed in Example 1 without the ratio of polycaproamide to polystyrene was changed to 40:60, and having the same fineness and length with polyvinyl chloride fibers.

The web was contacted for about 20% on the surface area in hot water at C., and then dried in air at C.

A dimethyl formamide solution consisting of a mixture of 6% polyurethane elastomer, which was produced from the reaction of polyethylene propylene adipate (molar ratio of ethylene glycol unit to propylene glycol unit 0.7:0.3) having a molecular weight of 1500 and hydroxyl groups at both ends, p.p-diphenylmethane diisocyanate and ethylene glycol (molar ratio of 1:2.5:1.5) and 5% based on the weight of said elastomer of ethyl cellulose octadecyl urethane was impregnated into the web.

The amount of the bonding inhibitor, i.e. ethyl cellulose octadecyl urethane, was reached to about 4% by weight of the web fibers.

The web was dipped into an aqueous solution containing 30 weight percent of dimethyl formamide for 15 minutes to complete the coagulation of the impregnated elastomer. The web was then squeezed with rollers, and thoroughly washed with water. It was pressed between hot rollers at 100 C. to smoothen the surface of the web and dried. Then the sheet thus obtained was dipped into hot toluene warmed at 70 C. for 5 hours to remove ethyl cellulose octadecyl urethane and polystryrene, which was a component of the web fiber, and washed with methanol and with water and then dried.

The adhesions among the web fibers and the coagulated microporous elastomer were substantially not seen by the examination under the high powered microscopy.

The sheet, thus obtained, was very soft and had a fine appearance like a soft leather for clothes. Its characteristics are shown in the next table showing the similar value to sheep leathers.

The Sheep Italian Item (unit) invention (suede) sheep Weight (g./m. 306 269 218 Thickness (mm.) 0. 69 O. 58 0. 64 Apparent specific gravity (kg./

mm. 0. 45 0. 51 0. 34 Tensile strength (kg/mini). 1. 10 1. 35 0. 30 Elongation (percent) 75. 39. 44. 9 Tear strength (kg). 3. 0 l. 4 2. 0 Surface wear (times).

1 500 Rubbing resistance (times). 5,000-81000 Hardness 1 45 Moisture content (percent) 14 14 Moisture absorption (pereen 165 143 225 Water resistance 2 (em.) 27 53 Gas permeability 3 (see) 47 19 48 Moisture permeability (g/.rn. /24

hrs.) 4, 590 8, 220 8,310

1 The length of a sample piece of 15 mm. breadth when pushed horizontally until its tip comes in contact with a slope of 45.

2 Hydraulic pressure before water begins to leak (JISP-8117) 1903.

3 Time required for forcing out a definite volume of air (JISZ-0208).

When a grain side is formed in this sheet by the method disclosed in Example 1 of US. Patent No. 3,190,766, the coated sheet material, thus obtained was useful as a synthetic leather like a box-calf for shoe-upper.

EXAMPLE 5 The same web disclosed in Example 3 was impregnated with a tetrahydrofuran solution of a mixture consisting of 8% polyurethane elastomer, which was produced from the same reaction discolsed in Example 3, and 10%, based on the weigth of said elastomer, of sorbitan monopalmitate. Excess solution was squeezed out between pressure rollers so that about 0.8 part by weight of polyurethane elastomer was retained in each part by weight of the web. The amount of the inhibitor in the Web was reached to about 10% by weight of the web.

The impregnated web was dipped into an aqueous solution of 40 weight percent tetrahydrofuran for 10 minutes to coagulate the impregnated elastomer, and further treated in water for 5 minutes to complete the coagulation of the elastomer. It was squeezed by pair of rollers and dried.

Then, the inhibitor was removed by hot toluene. The web was washed with methanol and then with water and dried.

The sheet material, thus obtained, had supple, vaporand moisture permeability as well as compact feeling, and this material was the useful for the base substrate to produce a synthetic leather like cow-hide by coating said sheet material with dimethyl formamide solution of polyurethane elastomer and then coagulating it in water and drying.

EXAMPLE 6 The web having the Weight of 300 g./m. which was produced by same process disclosed in Example 3, was dipped into methanol solution consisting 5 weight percent of stearyl alcohol, then sufficiently squeezed and dried at 80 C. The amount of the inhibitor in the web was reached to about 8 weight percent by weight of the web.

A dimethyl formamide solution containing a mixture of 6% polyurethane elastomer, which was produced from the reaction of polytetramethylene glycol, p.p-diphenylmethane diisocyanate and p.p-methylene dianiline by the method disclosed in US. Patent No. 2,929,800; and 5% based on the weight of said elastomer, of ethyl cellulose octadecyl urethane. Excess solution was squeezed out between pressure rollers so that about 0.6 part by weight of polyurethane was retained in each part by weight of the web. The total amount of the inhibitors were reached to about 11 percent by weight of the Web.

The impregnated web was dipped into an aqueous solution of 30 weight percent of dimethyl formamide for 10 hours for coagulation of said elastomer, then further dipped into water for 5 minutes to complete the coagulation of the elastomer. The web was squeezed with rollers, thoroughly washed with Water, pressed with rollers at .C., and dried.

Said sheet material was dipped into hot methanol for 3 hours to remove stearyl aclohol, washed with water and then dried.

The sheet material, thus obtained, had a good suppleness, vaporand moisture permeability.

EXAMPLE 7 The web having the weight of 450 g./m. which was produced by the same method disclosed in Example 1 without the components of the fiber changed to 40 weight percent of polycaprolactam and 60 weight percent of polystyrene, was dipped into toluene at 70 C. to remove polystyrene from the fiber. The web, thus obtained, was consisted with the perforated polycaproamide fibers and having the weight of g./m.

The web was dipped into an aqueous emulsion comprising ethyl cellulose octadecyl urethane, which emulsion was same as in Example 2 and then dried.

A dimethyl formamide solution containing a mixture of 15 weight percent of polyester urethane elastomer, which was produced from the reaction of polyethylene propylene adipate (molar ratio of ethylene glycol unit and propylene glycol unit of 9:1) having a molecular weight of 2000, p.p'-diphenylmethane diisocyanate and ethylene glycol (molar ratio 1:5 :4), and 4%, based on the weight of said elastomer of sorbitan monostearate, was impregnated into the web.

The total amount of the inhibitors were reached to about 8 percent by weight of the Web.

The impregnated web was then dipped into an aqueous solution of 50 Weight percent dimethyl formamide for 30 minutes to coagulate the impregnated elastomer. The web was pressed with rollers, washed with water, and dried.

The web was treated with toluene for 3 hours to remove the inhibitors, washed with water and then dried.

The suppleness, the textures and the appearance of the sheet material, thus obtained were superior to those of the sheet material, in which any inhibitor was not used in the preparation of said material.

Surface decoration may be applied to the sheet materials of the examples. Coloring, lustering and smoothing on the surface may be effected by such processes as dyeing, spraying or coating a layer of dissolved or emulsified high molecular substance or pattern printing or embossing and the like.

We claim:

1. In a method of manufacturing a supple, vaporand moisture permeable sheet material comprising the steps of impregnating a needle punched web throughout with a solution of polyurethane elastomer, coagulating said impregnated elastomer with a non-solvent for said elastomer and said web, said non-solvent being miscible with the solvent of said elastomeric solution, washing the sheet material with water to remove the residual solvent in the coagulated elastomer and drying said sheet material,

the improvement which comprises treating the needle punched web with 0.1 to 20 weight percent, based on the web, of a bonding inhibitor, which is selected from the group consisting of (a) saturated aliphatic hydrocarbons having 12 to 30 carbon atoms in the molecule, (b) saturated aliphatic alcohols having an alkyl group of 12 to 30 carbon atoms in the molecule, (c) carboxylic acid esters having at least one saturated alkyl group of 12 to 30 carbon atom in the molecule, and (d) urethanes having at least one saturated alkyl group of 12 to 30 carbon atoms in the molecule, and removing said bonding inhibitor after the step of coagulating the impregnated elastomer.

2. In the method of claim 1, wherein the needle punched web is pretreated with a bonding inhibitor prior to the step of impregnating said web with the solution of said elastomer.

3. In the method of claim 1, wherein the needle punched web is treated with a bonding inhibitor simultaneously with the step of impregnating said web with the solution of said elastomer.

4. In the method of claim 1, wherein the bonding inhibitor is stearyl alcohol.

5. In the method of claim 1, wherein the bonding inhibitor is sorbitan monostearate.

6. In the method of claim 1, wherein the bonding inhibitor is sorbitan monopalmitate.

7. In the method of claim 1, wherein the bonding inhibitor is ethyl cellulose octadecyl urethane.

8. In the method of claim 1, wherein the bonding inhibitor is paraffin wax.

9. In the method of claim 1, wherein said web comprises the fiber consisting of the mixture of about 33 to 60 percent by weight of polyamide and about 67 to 40 percent by weight of polystyrene, and polystyrene, a component polymer of said fiber, is removed at the step of removing the inhibitor.

10. In the method of claim 1, wherein said web comprises the fiber consisting of the mixture of about 33 to 60 percent by weight of polyester and about 67 to 40 percent by weight of polystyrene, and polystyrene, a component polymer of said fiber, is removed at the step of removing the inhibitor,

11. In the method of claim 1 wherein the needle punched web is treated with a bonding inhibitor simultaneously with the step of impregnating said web with the solution of said elastomer, said bonding inhibitor being selected from the group consisting of (c) carboxylic acid esters having at least one saturated alkyl group of from 12 to 30 carbon atoms in the molecule and (d) urethanes having at least one saturated alkyl group of from 12 to 30 carbon atoms in the molecule which urethanes are the reaction product of monoisocyanate and alcohol.

References Cited UNITED STATES PATENTS 2,050,239 8/1936 Albright et al. 117-6 3,000,757 9/1961 Johnson et a1 117-63 3,067,482 12/1962 Hollowell 1l7-63 3,113,886 12/1963 Kolb.

3,169,885 2/1965 Golodner 117-63 3,190,766 6/1965 Yuan 117-63 3,208,875 9/1965 Holden 117--63 3,222,208 12/ 1965 Bertollo 11763 3,238,055 3/1966 Brightwell 117--63 3,296,016 1/1967 Murphy 117-63 3,377,190 4/1968 Baguley 117-63 WILLIAM D. MARTIN, Primary Examiner W. R. TRENOR, Assistant Examiner US. Cl. X.R. 

